This is a pair of modules that Maplin was selling some time back, to send stereo audio over a 2.4GHz radio link. The transmitter identifies as a USB sound card, I’ve personally used these units to transmit audio about 60ft. The transmitter, above, has a single button for pairing with the receiver below.
Receiver
The receiver unit has a large external antenna, a link status LED & volume buttons, these directly control the volume level on the host PC via the sound card drivers.
Receiver PCB Top
Popping the case open on the receiver reveals a large PCB, holding the chipset, along with the audio output jacks & Mini-USB power input. The antenna Coax is soldered to the PCB.
Receiver PCB Bottom
The top of the board has the control buttons, and the status LED.
Receiver Chipset
The chipset used here is a Nordic Semiconductor nRF20Z01 2.4GHz Stereo Audio Streamer, there’s a small microcontroller which does all the register magic on the RF transceiver. The RF chain is at the top of the photo, audio outputs on the top left, and the micro USB power input & voltage regulators at bottom left.
Transmitter PCB Top
The transmitter PCB has a Sonix USB Audio Codec, to interface with the host PC. This is then fed into another Nordic Semi part on the opposite side of the board:
Transmitter PCB Bottom
The bottom of the transmitter has the RF section, and another small control microcontroller.
I recently came across these on eBay, so I thought I’d grab one to see how they function, with all the metrics they display, there’s potential here for them to be very useful indeed.
One of the best parts is that no wiring is required between the sensor board & the LCD head unit – everything is transmitted over a 2.4GHz data link using NRF24L01 modules.
Above is the display unit, with it’s colour LCD display. Many features are available on this, & they appear to be designed for battery powered systems.
Monitor PCB
Another PCB handles the current & voltage sensing, so this one can be mounted as close to the high current wiring as possible.
Monitor PCB Microcontroller
The transmitter PCB is controlled with an STM8S003F3 microcontroller from ST Microelectronics. This is a Flash based STM with 8KB of ROM, 1KB of RAM & 10-bit ADC. The NRF24L01 transceiver module is just to the left.
There’s only a single button on this board, for pairing both ends of the link.
Output MOSFET
The high current end of the board has the 0.0025Ω current shunt & the output switch MOSFET, a STP75NF75 75v 75A FET, also from ST Microelectronics. A separate power source can be provided for the logic via the blue terminal block instead of powering from the source being measured.
LCD Unit Rear
Here’s the display unit, only a pair of power terminals are provided, 5-24v wide-range input is catered for.
LCD Unit PCB
Unclipping the back of the board reveals the PCB, with another 2.4GHz NRF24L01 module, and a STM8S005K6 microcontroller in this case. The switching power supply that handles the wide input voltage is along the top edge of the board.
Unfortunately I didn’t get any instruction manual with this, so some guesswork & translation of the finest Chinglish was required to get my head round the way everything works. To make life a little easier for others that might have this issue, here’s a list of functions & how to make them work.
LCD Closeup
On the right edge of the board is the function list, a quick press of the OK button turns a function ON/OFF, while holding it allows the threshold to be set.
When the output is disabled by one of the protection functions, turning that function OFF will immediately enable the output again.
The UP/DOWN buttons obviously function to select the desired function with the cursor just to the left of the labels. Less obviously though, pressing the UP button while the very top function is selected will change the Amp-Hours display to a battery capacity icon, while pressing DOWN while the very bottom function is selected will change the Watts display to Hours.
The round circle to the right displays the status of a function. Green for OK/ON Grey for FAULT/OFF.
OVP: Over voltage protection. This will turn off the load when the measured voltage exceeds the set threshold.
OPP: Over power protection. This function prevents a load from pulling more than a specified number of watts from the supply.
OCP: Over current protection. This one’s a little more obvious, it’ll disable the output when the current measured exceeds the specified limit.
OUT: This one is the status of the output MOSFET. Can also be used to manually enable/disable the output.
OFT: Over time protection. This one could be useful when charging batteries, if the output is enabled for longer than the specified time, the output will toggle off.
OAH: Over Amp-Hours protection. If the counted Amp-Hours exceeds the set limit, the output will be disabled.
Nom: This one indicates the status of the RF data link between the modules, and can be used to set the channel they operate on.
Pairing is achieved by holding the OK button, selecting the channel on the LCD unit, and then pressing the button on the transmitter board. After a few seconds, (it appears to scan through all addresses until it gets a response) the display will resume updating.
This function would be required if there are more than a single meter within RF range of each other.
I’ve not yet had a proper play with all the protection functions, but a quick mess with the OVP setting proved it was very over-sensitive. Setting the protection voltage to 15v triggered the protection with the measured voltage between 12.5v-13.8v. More experimentation is required here I think, but as I plan to just use these for power monitoring, I’ll most likely leave all the advanced functions disabled.
Unfortunately the manual for the eBay GY561 Frequency & RF Power Meter is very badly translated, but I think I have figured out the calibration procedure, so here it goes 🙂
Initial Screen
On removing the front cover, which is just clipped on, there are 4 buttons. The only button that is usually available is the one on the far right, the power button.
I will term these buttons A, B, C, D, starting from the left side.
To get into the initial calibration screen, in the above image, hold button A while the power button (D) is pressed. Release the power button (D), then release button A.
The meter will show the screen above, where the frequency to calibrate can be chosen. This goes in 5MHz steps, 0-500MHz, using the B button to go down in frequency, and the C button to go up.
Once you’ve selected the frequency you wish to calibrate against, press button A, and the following screen will appear:
Frequency Calibration Screen
On this screen, the actual calibration can be done.
The number in the bottom left signifies the power level setting, from 1-5. The centre number is the calibration setting in Watts. The D in the bottom corner signifies that the setting is at the factory default.
Button C will cycle through the power level settings, for 2W, 5W, 10W 20W, 40W. This allows calibration at different power levels per frequency.
Once you have the frequency to calibrate, and you’ve selected the power level to calibrate at, connect a known RF power source to the input of the unit.
At this point, key the transmitter, and press button A. The display will change to the following:
Calibration Stage 2
When on this screen, you can set the power level of your RF source. Use the A key for +0.1W, the B key for +1W, and the C key for +10W.
Once you’ve keyed in the power of your source, press button D to save the setting. The “S” in the bottom corner will change to a “C”, to indicate a user calibration has been entered:
Calibration Complete
If you make a mistake with entering the power level, press the “C” key to cycle up to 60W, once at this level, another press of the button will reset the reading to zero. You can then enter the power level again.
If you wish to revert a user-entered setting to the factory default, press button B on the page above. The “D” will reappear in the bottom corner to indicate the setting has been restored.
At this point you can either press button C to calibrate at another power level for this frequency, or press button D to go back to the frequency selection.
Press button D again when at the frequency selection page to turn the unit off. The unit will then power up normally next time the power button (D) is pressed.
This is an old legacy wireless mouse from Logitech. This uses a ball rather than optical technology.
Bottom
Bottom of the mouse, showing the battery cover & the mouse ball.
PCB Bottom
Top removed from the mouse, showing the PCB inside. The smaller PCB on the left supports the microswitches for the buttons & mouse wheel.
Switches
Closeup of small PCB showing the microswitches & the IR LED & phototransistor pair for the mouse wheel encoder.
Main PCB
View of main PCB, with interface IC lower right. Pair of quartz crystals provide clocking for the transmitter & internal µC.
Battery contacts are on lower left of the PCB. At the top are the IR pairs for the X & Y axis of the mouse ball.
Encoder Pairs
Closeup of the pairs of IR LEDs & phototransistors that make up the encoders for X/Y movement of the mouse, together with the slotted wheels in the mouse base that rotate with the ball. Steel wire around the smaller PCB is the antenna.
Here is a Marmitek Gigavideo 30 2.4GHz wireless video transmitter, has a receiver paired which will be uploaded shortly. Here is a view of the antennae, the large flat one being the 2.4GHz directional, the whip antenna possibly performing IR relay functions for the remote control.
Bottom Label
For all those interested, here’s the bottom label.
PCB Top
The top cover removed reveals the main PCB. Big metal can is the RF transmitter circuitry. was encapsulated circuitry below that looks like an FM modulator for the whip antenna. Big TO220 package on heatsink is a LM7805 5-Volt regulator for the transmitter module.
These units work fantastically well when the antennas are aligned properly, at a decent range, however, they do have a nasty habit of doubling as a very effective WiFi LAN jammer.
This is the Current Cost CC128 Real Time Power Meter. Shown here is the display unit, British Gas issued these free to some customers.
This unit measures current power draw in Watts, cost of power currently being used (requires unit price to be set), overall kWh usage over the past 1, 7 or 30 days & power trends during the day, night & evening. Also displays current time & current room temperature.
Display PCB
Here the front panel of the display has been un-clipped. At the bottom are the RJ-45 serial port & power connections.
This unit uses a PIC micro-controller as it’s CPU (PIC18F85J90) Just above & left of the CPU is the 433MHz SPD radio receiver module. The chips on the right of the CPU are a 25LC128 SPI serial EEPROM for data storage & a 74HC4060 14 stage binary counter, to which is connected the 32kHz clock crystal. The red wire around the top of the display is the antenna for the radio receiver.
For more info on the CC128 in general, the serial port & software for computer data logging, see this link
See this link for Current Cost’s list of software
Processor & Radio
Closeup of the ICs on the mainboard.
Transmitter Unit
Here we have the transmitter unit, with Current Transformer (CT). The red clamp fits around one of the electric meter tails & read the current going to the various circuits. This unit is powered by 2x D cells, rated at a life of 7 years.
Transmitter PCB
The PCB inside the transmitter. Again very minimal design, unknown controller IC, 433MHz radio transmitter on right hand side with wire antenna. Two barrel connectors on left hand side of board allow connection of up to two more CT clamps for measurement of 3-phase power. Centre of board is unmarked header. (ICSP?)
Current Transformer
CT unit. Inside is a coil of wire & an iron core which surrounds the cable to be measured.
PIC18F85J90
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